Well, I didn’t do a good job of dividing up this section. I cut off the first verse of the thought unit, so here it is: 24Οὐδεὶς δύναται δυσὶ κυρίοις δουλεύειν: ἢ γὰρ τὸν ἕνα μισήσει καὶ τὸν ἕτερον ἀγαπήσει, ἢ ἑνὸς ἀνθέξεται καὶ τοῦ ἑτέρου καταφρονήσει: οὐ δύνασθε θεῷ δουλεύειν καὶ μαμωνᾷ.
The δια τουτο in v. 25 indicates that this whole section is an expansion of the brief command and statement in v. 24. I’m going to propose what may be a novel metaphor for understanding the “two masters.” I recognize that this is somewhat speculative, but I think it’s worth exploring. Most of us are acquainted with the idea of Feudalism, the reciprocal pledge between lord and vassal. The vassal supports the lord while the lord (supposedly) protects the vassal. Such notions grew directly out of the practice of comitatus, Germanic warrior covenants, known in the 1st century AD. The Hittite suzerain-vassal treaties which served as a template for Deuteronomy expressed the same basic idea. So, this concept was familiar enough to people of the 1st century.

I think that this martial relationship may explain the passage better than domestic slavery. The vassal depends on his lord for security, which is the thought Jesus seems to be expressing. The idea is not so much that money would tell someone what to do like an aristocrat orders a slave, but that in order to gain the security which people think money will supply, they give themselves over to it. Choosing which master to “hate” rather than “love,” or “cling to” rather than “disregard” does not seem to be something within a domestic’s slave’s sphere of choice; however, one might picture a small kingdom between two larger kingdoms having to choose which side to support and seek protection from during a conflict.

In any case, whether domestic slavery or vassalship is intended, Jesus’ point is that worry is equivalent to serving another master. By seeking to secure one’s future through financial resources, a person moves under the wrong lord for protection. By doing so, he actually deprives himself of the security he seeks to obtain.

Quickly, I also want to notice this appeal to a “natural theology” of sorts. Jesus directs his audience’s attentions to the natural world, and from there extrapolates a conclusion about God’s relationship to his children (v. 30). Perhaps this testifies to the ability of a believer to meditate, not only upon God’s book of special revelation, but also upon his book of general revelation. At the very least, it shows us that for the believer, the natural world is not replaced but rather enhanced by becoming also a window into spiritual realities.